PATHOGENESIS AND TREATMENT OF APLASTIC ANEMIA

再生障碍性贫血的发病机制和治疗

• 批准号: 6432684
• 负责人: NEAL S YOUNG
• 金额: --
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6432684
• 关键词: aplastic anemia; artificial immunosuppression; autoimmune disorder; bone marrow disorder; clinical research; cytotoxic T lymphocyte; gene targeting; hematopoiesis; hematopoietic stem cells; hepatitis; histocompatibility typing; human subject; human therapy evaluation; immunohematology; lymphokines; paroxysmal nocturnal hemoglobinuria; phosphatidylinositols; tissue /cell culture

Aplastic anemia (AA) and other types of bone marrow failure have clinical and laboratory features consistent with an autoimmune pathophysiology, with a diversity of inciting antigens, including viruses, chemicals, and drugs. Whatever its specific etiology, a majority of patients respond with hematologic improvement after immunosuppressive therapies. One important clinical feature of AA is its evolution, sometimes years after normalization of blood counts, to other hematologic diseases such as paroxysmal nocturnal hemoglobinuria (PNH), which derive from clones of hematopoietic stem cells. Our laboratory studies have focused on the immune pathophysiology of AA, identification of a viral antigen, and the mechanism of late clonal evolution. Studies of etiology have continued to focus on an unknown hepatitis virus in the post-hepatitis AA syndrome (see Z01 HL 02319-14 HB). Current studies of the immune systems role in bone marrow suppression have focused on gamma-interferon (gamma-IFN), a lymphokine that inhibits hematopoiesis in vitro and in vivo. In our animal model for immune-mediated AA, congenic lymphocytes induce profound marrow aplasia, which can be abrogated by early administration of anti- lymphocyte globulin (ATG), cyclosporine, and monoclonal antibody to gamma-IFN. Current efforts are directed to producing chronic aplasia by periodic infusions of lymphoid cells, as well as determination of the specificity of the immune response. We have measured gamma-IFN in circulating and marrow lymphocytes using flow cytometry. About 2/3 of patients with severe AA and also with the diagnosis of hypocellular myelodysplasia shown the presence of this cytokine in blood T cells; less than 10% of recovered patients scored positive. The presence of the cytokine was highly predictive for response to immunosuppressive therapies: 16/16 patients whose cells contained gamma-IFN responded, compared to 4/12 patients whose blood lacked gamma-IFN; IFN declined after treatment, while IL-4 content increased. Recurrence of IFN intracellularly predicted relapse. Marrow intracellular IFN may be even better correlated with response. Measurement of surface gamma-IFN allows isolation of viable activated T cells, which may be useful in determining lymphoid clonality and characterizing and even identifying their antigens. Intracellular cytokine measurements indicating TH1/TH2 balance are also altered by in vitro treatment with cyclosporine, various androgen preparations, and growth factor combinations; stem cell factor and granulocyte colony stimulating factor also depress IFN expression in vivo in normal individuals undergoing stem cell mobilization. In other clinical studies in aplastic anemia, 24 patients with newly diagnosed severe aplastic anemia have now been randomized in a comparative protocol; the response rate has been higher for ATG than for high dose cyclophosphamide, but frank relapses and cytogenetic abnormalities have occurred only in the ATG arm. For children, our standard protocol has been modified to shorten the duration of cyclosporine therapy, begin cyclosporine is begun later in order to avoid abrogation of ATG tolerization, and the new immunosuppressive agent mycophenolate mofetil has been added, all in an effort to decrease the high relapse rate. In the laboratory, late clonal disease, both PNH and myelodysplasia, using sensitive flow cytometric and fluorescent in situ hybridization assays. Approximately 20% of patients with AA and probably a larger proportion of cases of hypocellular myelodysplasia present with evidence of a PNH clone. Our results are consistent with the hypothesis that PNH represents an escape mechanism in immune-mediated bone marrow failure, and that two steps are required for the development of PNH. Alternatively, a glycosylphosphoinositol- linked protein may be involved in the initial antigenic stimulation. - autoimmunity, T cells, bone marrow failure, myelodsyplasia, immunosuppression, interferon - Human Subjects

再生障碍性贫血(AA)和其他类型的骨髓衰竭具有符合自身免疫病理生理学的临床和实验室特征，具有多种激发抗原，包括病毒、化学物质和药物。无论其具体病因如何，大多数患者在接受免疫抑制治疗后，血液学有所改善。再生障碍性贫血的一个重要临床特征是，有时在血细胞计数正常化数年后，它会演变为其他血液疾病，如发作性睡眠性血红蛋白尿(PNH)，这些疾病源于造血干细胞克隆。我们的实验室研究主要集中在AA的免疫病理生理学、病毒抗原的鉴定以及后期克隆进化的机制上。病因学研究继续集中在甲型肝炎后综合征中的一种未知肝炎病毒(见Z01 HL 02319-14 HB)。目前对免疫系统在骨髓抑制中作用的研究主要集中在伽马-干扰素(伽马-干扰素)，这是一种在体外和体内抑制造血的淋巴因子。在我们的免疫介导型再生障碍性贫血动物模型中，同源淋巴细胞引起严重的骨髓再生障碍性贫血，早期应用抗淋巴细胞球蛋白(ATG)、环孢菌素和抗γ-干扰素的单抗可以消除这种再生障碍性贫血。目前的努力是通过定期输注淋巴样细胞以及确定免疫反应的特异性来产生慢性再生障碍性贫血。我们用流式细胞术检测了循环和骨髓淋巴细胞中的γ-干扰素。约2/3的重型再生障碍性贫血患者和诊断为少细胞骨髓发育不良的患者在血T细胞中存在这种细胞因子；在恢复的患者中，只有不到10%的患者获得阳性结果。细胞因子的存在对免疫抑制治疗的反应有很高的预测性：16例细胞含有伽马-干扰素的患者有反应，而12例血液中没有伽马-干扰素的患者有4例有反应；治疗后干扰素下降，而IL-4含量上升。细胞内干扰素复发预示复发。骨髓细胞内干扰素与应答的相关性可能更好。检测表面γ-干扰素可以分离活性激活的T细胞，这可能有助于确定淋巴克隆性，表征甚至识别其抗原。细胞内细胞因子测量表明，环孢素、各种雄激素制剂和生长因子组合的体外处理也改变了TH1/TH2的平衡；干细胞因子和粒细胞集落刺激因子也抑制了正在进行干细胞动员的正常人体内干扰素的表达。在再生障碍性贫血的其他临床研究中，24名新诊断的重型再生障碍性贫血患者现已被随机对照；ATG组的有效率高于大剂量环磷酰胺组，但坦率的复发和细胞遗传学异常仅发生在ATG组。对于儿童，我们的标准方案已被修改，以缩短环孢素治疗的持续时间，开始环孢素治疗的时间较晚，以避免废除对ATG的耐受性，并增加了新的免疫抑制剂霉酚酸酯，所有这些都是为了降低高复发率。在实验室，晚期克隆性疾病，包括PNH和骨髓异常增生症，使用灵敏的流式细胞术和荧光原位杂交分析。大约20%的再生障碍性贫血患者和可能更大比例的少细胞骨髓发育不良患者存在PNH克隆的证据。我们的结果与假设一致，即PNH是免疫介导的骨髓衰竭的一种逃逸机制，PNH的发展需要两个步骤。或者，糖基磷酸肌醇连接的蛋白可能参与最初的抗原刺激。-自身免疫、T细胞、骨髓衰竭、骨髓增生异常、免疫抑制、干扰素-人类受试者